It is known to make a thread package in the form of a cheese or bobbin by winding, i.e., a thread is wound onto a support or carrying member, e.g., a winding mandrel, spool or the like. Two winding methods are known, namely the so-called random winding and the precision winding. In the case of a random winding, the thread is wound onto a package, i.e., a bobbin or cheese peripherally driven by a driving cylinder, the thread being supplied by means of a grooved drum or a thread guide guided by a grooved drum and is placed on the package. The grooved drum is in constant rotary connection with the driving cylinder. However, this method only makes it possible to produce random windings, i.e., windings whose "turns ratio" decreases with the increasing package diameter, the pitch or helix angle of the thread laying device remaining constant. The term "turns ratio" is understood to mean the number of turns, i.e., revolutions, of the package per double stroke of the thread from the thread laying device. A "stroke" is the removal of thread from one end of the thread laying device to the other, so a double stroke comprises the thread removal from one end to the other end and then back to the starting end.
It is necessary when producing a precision winding that, in the winding machine, the thread laying device is connected in a positively engaged manner with the cheese or spool holder. The turns ratio of the cheese turns to the double stroke of the thread remains constant throughout the precision winding process, i.e., the pitch angle of the thread onto the cheese from the thread laying device changes and becomes more acute with increasing cheese diameter. In this winding method, the cheese is driven at its shaft and for obtaining a constant turns ratio the thread laying device is in positively engaging rotary connection with the cheese.
The two winding methods differ in various ways. Random winding is characterized by a constant pitch angle .alpha. of the thread laying device over the entire cheese diameter, which leads to a good dimensional stability and transportability. By the coupling of the driving roller and the thread laying system, a simpler mechanical construction of the traverse winding frame is obtained. Disadvantages result from unfavorable numbers of turns, which become noticable during the formation of the cheese at specific cheese diameters, constituting so-called images. A non-uniform yarn twisting results from these so-called image areas and this can subsequently lead to uncertain removal conditions. Due to the fact that the precision-wound cheese has no such image areas very good removal characteristics are obtained. As the pitch angle .alpha. of the thread laying device varies significantly during cheese formation, the dimensional stability is poor. Attempts have been made to obtain improved cheese stability involving considerable technical effort and expenditure (i.e., bobbin stirrup relief, blocking relief, etc.), but the results leave much to be desired.
Thus, in summarizing, it can be stated that precision winding leads to no problems with respect to the cheese removal characteristics, whereas considerable expenditure is involved regarding the cheese shape and construction, particularly in the case of large cheeses with elastic and bulky yarns (textured yarns). With random winding there are no problems regarding the bobbin construction, e.g., in view of the dimensional stability, but additional expenditure is required in connection with the cheese removal characteristics.
The problem of the present invention is therefore to so develop the winding machine of the aforementioned type so that the advantages of precision winding can be combined with those of random winding in such a way that it is possible to obtain a better cheese removal, dimensional stability and transportability of the cheese in a simple manner and with limited expenditure.